Device for truing the grinding wheels of grinding machines



Dec. 22, 1953 A. MOTTU DEVICE FOR TRUING THE GRINDING WHEELS 0F GRINDING MACHINES Filed Oct. 18, 1952 3 Sheets-Sheet 1 I AM n M i/M A fie/"n a Dec. 22, 1953 MOTTU 2,663,292

-DEVICE FOR TRUING THE GRINDING WHEELS OF GRINDING MACHINES F'iled Oct. 18, 1952 5 Sheets-Sheet 2 An0nf M07 24 A f/027% e v Dec. 22, 1953 A. MOTTU 2,663,292

DEVICE FOR TRUING THE GRINDING WHEELS OF GRINDING MACHINES Filed Oct. 18, 1952 3 Sheets-Sheet 3 FIG. 3

- In van/0M fi r/v/re M07791 Patented Dec. 22, 1953 DEVICE FOR TRUING THE GRINDING WHEELS OF GRINDING MACHINES Andr Mottu, Genthod-Bellevue, Switzerland, as-

signor to Societe Genevoise dInstruments de Physique, Geneva, Switzerland, a firm of Switzerland Application October 18, 1952, Serial No. 315,469

Claims priority, application Switzerland November 10, 1951 My invention has for its object a device for truing the grinding wheel of a grinding machine and it is chiefly applicable in the case of a threadgrinding machine.

Numerous devices have already been proposed for truing grinding wheels. One of these includes a suitably shaped cam adapted to impart a reciprocating movement to the tip of the diamond cutter, said movement being perpendicular to the axis of the grinding wheel, and being associated with a continuous translational movementshifting the diamond cutter along a line parallel with the axis of the grinding wheel, whereby the two associated movements cause the tip of the diamond cutter to produce the desired outline on the operative surface of the grinding wheel. This prior arrangement is generally secured to the table of a grinding machine in order to obtain the translational movement parallel with the axis of the grinding wheel, whereas the reciprocating movement produced by the cam is controlled by the rotary movement of the spindle of the machine.

This prior arrangement shows various drawbacks which are chiefly ascribable to the fact that the deformation of the diamond cutter tip, as it'wears very quickly, changes the outline generated by it on the surface of the grinding wheel and thereby the cutting operation is not performed under favourable conditions. As a matter of fact, when the diamond is shifted towards the axis of the grinding wheel, it operates through its tip, while it cuts through its sides when it moves away from the axis of the grinding wheel; this is illustrated in Figs. 6 and? of accompanying drawings which show the operative parts of the diamond in conventional machines, viz. the tip and the sides respectively, as shown by hatchings, said parts engaging the surface of the thread as mentioned hereinabove.

Now, my invention has for its object to remove such drawbacks. The machine as provided by my invention includes the usual diamond carried by a slider and submitted, with reference to the grinding wheel, to a movement which is constituted by the combination of a longitudinal shifting of the table and a reciprocating transverse shifting of the slider, both last mentioned shiftings being controlled by the rotation of the machine spindle. r

According to my invention, there are provided two cams acting selectively on the diamond for obtaining its reciprocation against the action of a spring with a different timing according to the direction of progression of the table, the

6 Claims. (Cl. 12511) substitution of the cams being produced automatically at the end of each stroke of the table in either direction and providing an operative inward stroke of the diamond along the sections of the outline to be sharpened that recede as they engage the diamond progressing with the table in the direction to be considered.

The substitution of these cams is preferably provided by two interengaging spiral wheels carried inside a casing secured between the headstock and the tail-stock centers on the table of the machine, one of said spiral wheels being controlled by the rotation of the spindle and being held against axial movement while the second spiral wheel is adapted to slide axially between two stops under the action of the first spiral wheel; the two cams arranged side by side and rigid with the second spiral wheel are arranged in a manner such that, according to the direction of rotation of the spindle and the corresponding direction of the movement of the table, one of said cams is selectively urged by the relative'axial thrust exerted between the spiral wheels into cooperation with the end of a pusher member sliding transversely and carrying at its free end the sharpening diamond outter, the outline of said cams being such that the diamond cuts in succession the two sides of the outline of the thread formed on the grinding wheel through an action directed permanently towards the axis of the grinding wheel, to cut one of the sides of the outline during the shifting of the table in a predetermined direction and the other side during the movement of the table in the opposite direction.

'As the outline on the surface of the grinding wheel is cut by the diamond only while the latter moves towards the axis of the driving wheel,

the wear of the diamond is reduced by reason of its operating only through its tip.

I have illustrated by way of example in accompanying drawings a preferred embodiment of my invention. In said drawings:

Fig. l is a plan view of the table of a machine intended for the truing of threads, said view showing in horizontal cross-section the truing device according to my invention.

Fig. 2 is a vertical partial cross-section through the axis extending through the head-stock and tail-stock of the machine.

Fig. 3 is a side view of the cam structure.

Figs. 4 and 5 illustrate the paths followed by the diamond for executing the outline of the 0perative surface of the grinding Wheel.

Figs. 6 and 7 illustrate, as disclosed herein- \I above, the operation of a diamond cutter machining on a grinding wheel in conventional systems.

Fig, 8 is an elevational view of: the machine illustrating schematically the reversing means of the direction of progression of the table.

Turning to Fig. 1, l designates the head-stock of the grinding machine, said. head-stockbeing carried by the movable table 2 and incorporating the spindle 2 (Fig. 2) driven by a motor that is not illustrated. A center 3" and adriving. plate 4 provided with a dog 5 are rigid with .the spindle and revolve integrally therewith. 33 designates the actual grinding wheel to be trued, the axis of which, that is not illustratedrin Fig. l, isparallel with that of the spindle 24.

The table 2 also carries the tail-stock it provided with a center 1 coaxial with the center 3 of the head-stock.

The truing device includes a casing 34 secured to the table 2 by means of a screw 35 and clamped between the centers 3 and engaging the centerholes and lfia in two stationary spindles-9 and 39' rigid with the casin -.34;

A pinion 8 is revolubly, carried by the spindle 9, rigid with the casing, andiis prevented from being axially shifted, by, a shoulder 9a of the spindle 9. and by a-sleeve 31, secured to the casing 34. This pinion 8 is driven by the dog and transmits the rotation thusimparted to :it to another pinion i I carryingside by side two camsi2 and i3that are held fast on said pinion-orspi-ra'l wheel by a nut l4- anda key 3E engaging. the spiral wheel. The came [2 and i3, theoutline of which is: shown .in Fig.3 which is a side" view thereof, are intended for theproduction of a reciprocating movementof the-diamond it: which latter is rigid with a rod [6' sliding in the "bearing H'rigidwith the casing. Therod l6 thatis urged towards the cams l2 and l3 by a springvlfi carries, at its end facing 'the'loc'ation of thecams', a, pusher member [9 bearing against: the'cam registering selectively with saidrod as disclosed hereinafter.

The pinion or spiral'wheel llisfitted on a sleeve 28 and may revolve round the latteri'while it is held axially against shifting thereon; said sleeve 25 is provided with inner longitudinal grooves. inside whichmay run balls 2| bearing against the surface of the-spindle 22 rigid'with the casing. The-sleeve wand the wheel'l l may thus slide axially with slight friction over: said spindle 22. The pinions OILWhGC-IIS Sand H carry a series of helical teethand consequently, accorde ing to the direction of rotation of the-'wheel 8", the wheel I! is urged into axial movement in either direction. Its axialstroke is limited by the fact'that the sleeve abuts on the left-hand side against the casingfi iof the deviceand on the right hand side against a bearing22a'onthe spindle 22. At each reversalofithe. rotary move ment' of'the spindle 24 and consequentlyofthe direction of progression of the table 2, the wheel H is shifted axially so asto move the cam system and to bring one of the cams in front of the pusher member 59, which latter is urged against the said cam by the spring l8; each cam is'thus operative with reference to'said pusher member selectively according to the directionof progres sion of the table 2.

Fig. 2 shows anarrangementiwhich' allows a translational movement of the table while the diamond l5 executes its reciprocating movement through the'selective action of the cams l2and l3. The spindle 2'4 controlled by any suitable or known means, that need not be illustrated, drives a toothed wheel 25 meshing in its turn with a toothed wheel 26 driving in its turn a leading screw 21' theaxis of which is stationary with reference to the table the leading screw 21, as it revolves round its axis, screws into a nut 28 rigid with the frame of the machine 29; saidfram'e being provided with slideways, not illustrated, that serve for guiding the table 2. This produces a shifting of the table 2 over the frame.

Fig. 4 shows in dotted lines at 3B the path followed by the diamond cutter I5 when the table moves from left to right. The diamond cutter engages: the grinding wheel 33 under the action of the thrust exerted by the cam I 2 and sharpens the left h'and'sides of all the indentations of the outline of the grinding wheel, the shape of the cam being such that the diamond recedes speedily without engaging an point of the right hand 'sidesof said indentations;

When all:the left hand'sides-of the .outlineto be'sharpened on @the grinding wheel havewb'een trued, the movement of the spindle 24 and-consequently that of the table 2 are'reversed-andtthe right hand sides-of the outline, as-illustrated in Fig. 5, are cut by the diamond which follows-the path shown at 32. After reversal, the cam- 13 is substituted for the cam |-2- andiimparts tothe diamond a reciprocating movement ina directicn perpendicular to. the axis of the grinding wheel, the shifting-of the cams, substitutingthe cam 12 for the cam l3, beingoperatednautomatically' assoon asthe spindle-24 has reversed its direction of. rotation, by reason of therelative thrust exerted between :the two spiral-wheels 8 and Hand urging th'elatterwheel, towards (or away from) thewheel- 8;-

The outline of the cam I3 is such that-it produces a'reciprocatin'g 'movementiof the diamond that is thenreverse of that produced by thecam I2. Obviously the number of: reciprocations of the table depends on the conditions o'f operation.

The cutting or truing of the grinding wheel 3-3-is thus performed for each direction of movement of the table only from 'theroutside-of the grinding wheel towards the inside and-conse quently, the wearrof the diamond I5 is greatly reduced,- the tip "alone. of said diamond being-used and operating always under the best conditions of operation.

The reversalrof the direction of rotation ofithe spindle 24 and the consequenttchange inithe di rection of progression-of the table- 2, which are provided simultaneously, are obtained through means schematically illustratedsin Fig. 8. Stops 40 and 4!, carried by the'table 2, define theends of the travel of said table, said stops actuatea switch 42 reversing the direction of rotation of the motor driving the spindle. 24; these stops, the positions of which should be adjustable, are located in a mannersuch that the reversal of the direction of. operation may berobtainedat the endof each stroke for a position for whichthe diamond is entirely released. with reference to the grinding wheel;

The outlines of. the c'ams lz and l3=andfitheir angular setting are designedin' a manner" such that for this reversal position, the pusher: member I9 may-be shiftedf smoothly from one: cam onto the other, withoutimeetinganyobstacle. The suitableangular setting of the cams' is'provided by insertion of thekey 36.

A special set of cams is:- furnished for. each outline to be provided for the thread on the grinding wheel. Furthermore, it is necessary, for each different pitch of thread, to modify the ratio betweenthe speeds of the spindle and of the table. This is done by changing the ratio of reduction gearing between the wheels and 26, a special set of wheels being used for each difierent pitch to be obtained.

What Iclaim is: I

1. In a grinding machine, comprising a grinding wheel, a head-stock and atail-stock the common axis of which stocks is parallel with the axis of the grinding wheel, a table adaptedto move longitudinally in a direction parallel with the axis of the headand tail-stock and carrying said headand tail-stock, and a lead screw operatively connected with said table for controlling its longitudinal reciprocation; a device adapted to true the grinding wheel and including: a casing located between said headand tail-stock, a cutter-holder mounted in said casing so as to reciprocate in a direction perpendicular to the axis of the headand tail-stock, a cutter carried by said cutter-holder, two rotary and axially movable cams operatively connected with said lead screw and adapted to selectively engage the cutter holder to impart thereto intermittently a movement towards the axis of the grinding wheel to true the outline thereof, a spring urging the cutter back during theidle periods of the rotation of the operative cam and means controlling the axial displacements of said cams, said means being actuated by the change of direction of rotation of said lead screw for urging axially the corresponding cam into position to provide the cutter progressing with the table in the direction to be considered.

2. In a grinding machine comprising a grinding wheel, ahead-stock and a tail-stock the common axis of which stocks is parallel with the axis of the grinding wheel, a table adapted to move longitudinally in a direction parallel with the axis of the headand tail-stock and carrying said headand tail-stock, a lead screw operatively connected with said table for controlling its longitudinal reciprocation; a device adapted to true the grinding wheel and including: a casing located between said headand tail-stock, a cut-- ter-holder mounted in said casing so as to reciprocate ina direction perpendicular to the axis of the headand tail-stock, a cutter carried by said cutter-holder, two rotary and axially movable cams operativelyconnected with said lead screw and adapted to selectively engage the cut ter-holder to impart thereto intermittently a movement towards the axis of the grinding wheel to true the outline thereof, a spring urging the cutter back during the idle periods of the rotation of the operative cam, a first helical wheel in permanent driving connection with the lead screw and coaxial therewith, means preventing the axial shifting of the first helical wheel, a sec ond helical wheel rigid with'said cams and in permanent engagement with the first helical wheel, the axis of said helical wheels being parallel with that of the headand tail-stock, said second helical wheel being axially shiftahle in either direction under the action of the relative thrust exerted between the helical wheels according to the direction of revolution of the lead screw, whereby said cams are axially shifted and are brought selectively into register with the an operative inward stroke of cutter holder for engagement therewith accordcal wheel under the action of the revolution of the lead screw in either direction;

3. In a thread-grinding machine comprising a grinding wheel the edge of which assumes transversely a threaded outline, a head-stock and a tail-stock the common axis of said stocks being parallel with the axis of thegrinding wheel, a table adapted to move longitudinally in a direction parallel with the axis of the headand tailstock and carrying said headand tail-stock, and

'a lead screw the axis of which is parallel with that of the grinding wheel, operatively connected with said table for controlling its longitudinal reciprocation; a device adapted to true the grinding wheel and including: a casing secured to the table between the two stocks, a cutter-holder adapted to reciprocate inside said casing in a direction radial with reference to the grinding wheel, a cutter for the grinding'wheel carried by said cutter-holder, a spring urging said holder away from the grinding'wheel, two interengaging helical wheels revolubly carried inside the casing and the axes of which are parallel with the axis of the grinding wheel, means whereby the lead screw controls the rotation of the first helical wheel, means for preventing the axial shifting of the first helical wheel, means whereby the second helical wheel is adapted to slide longitudinally on its axis, means whereby the lead screw controls the progression of the table, means whereby the lead screw is constrained to revolve alternatinglyin either direction, two cams fitted side by side over the second helical wheel in planes adapted to register selectively with the axis of the cutter-holder according to the axial position assumed by the second helical wheel under the action of the thrust exerted in either di rection on the latter by the revolving first helical wheel and a pusher member rigid with the cutter-holder and urged by the spring acting on said holder against the cam registering with the axis of the cutter-holder, the operative section of each cam being adapted to produce an outward movement of the cutter-holder against the action of its spring during the registering with the cutter of the surfaces of the threaded outline of the grinding'wheel that face a predetermined axial direction.

4. In a thread-grinding machine comprising a grinding wheel the edge of which assumes transversely a threaded outline, a head-stock and a rection radial with reference to the grinding wheel, a cutter for the grinding wheel carried by said cutter-holder, a spring urging said holder away from the grinding wheel, two interengaging helical wheels revolubly carried inside the casing and the axes of which are parallel with the axis of the grinding wheel, means whereby the lead screw controls the rotation of the first helical wheel, means for preventing the axial shifting of the first helical wheel, means whereby the second helical wheel is adapted to slide longitudinally of its axis, means whereby the spindle is constrained to revolve alternatingly in either di rection, a set of two'cams removably fittedside by-side over the second helicalwheel in planes adaptedto, register selectively with the axis of the. cutter-holder according to the axial position assumed by the second helical wheelunder the action of the thrust exerted'in either direction on the latter by the revolving first helical wheel and a pusher member rigid with the cutter-holder and urged by the spring acting on said holder against the. cam registering with theaxis of the cutter-holder, the'operative section of each cam being adapted to, producean outward movement ofthecutter-holder against the action of its spring during the registering with the cutter of the surfaces-of the threaded outline of the grinding wheel that face a predetermined axial direction.

5., In a thread-grinding machine comprising a grinding wheel the edge of which assumes transversely a threaded outline, a head-stock and a tail-stock, the common axis of said: stocks being parallel with the axis of the grinding wheel, a table adapted'to move longitudinally in a direction parallel with the axis of the headand tail-stock and carrying said, headandtailstock, and a leadscrew the axis of which is parallel with that of' the grinding wheel, operatively connected with'said table for controlling its longitudinal reciprocation; adapted to true-the grinding wheel and including: a casing secured to the table between the two stocks, a cutter-holder adapted to reciprocate insidesaid casing ina direction radial with reference to thegrinding wheel, a cutter for the grinding wheelcarriedby said cutter-holder, a spring urging said holder away from the grind ing wheel, two interengaginghelical wheels revolubly carried inside the casing andthe axes of which are-parallel with theaxis: of the grinding wheel, means whereby the lead screw controls the rotation of the first helical wheel, means for preventing the axial shifting of the first helical wheel, means-whereby the. second helical wheel is adapted to slide longitudinally of its axis, means whereby the spindle is constrained to revolve alternatingly in either direction; a set of two cams removably fitted side by side over the secondhelical wheel in planes adapted to register selectively withthe axis of the cutterholder according to'the axial position assumed by the second helical wheel under the action of the thrust exerted in either direction onthe latter by the revolving first helical wheel, a pusher member rigid with the cutter-holder and urged by the spring acting on said holder against the cam registering with the axis. of' the cutter holder, the. op rative section of each cam bein adapted to produce an outward movement of the cuttenholder againstv the action of. its spring during the registering with the cutterof the surfaces of the threaded outline of the grinding wheel that face a predetermined axial direction,

. .and means for reversing the direction of. rotaa device 2 tion of the spindle at each end of the stroke of thetable.

6.- In a thread-grinding machine comprising a grinding'wheel the edge of which assumes transversely a threaded outline, a head-stock and a tail-stock, the common axis of saidstocks being-parallel with'theaxis of the grinding wheel, a table adapted to move longitudinally in a direction parallel with the axis of the head and tail -stock and carrying said headand tailstock, anda leadscrew the axis of which is parallel with that of the grinding wheel, operatively connected with said table for controlling its longitudinal reciprocation; a device adapted to true the grinding wheel and including: a casing secured .tothe table between the two stocks, a cut tereholder' adapted to reciprocate inside said casing in adirection radial with reference to thegrinding, wheel,qa cutter for the grinding Wheel carried by Said cutter-holder, a spring urging said holder away from the grinding wheel, two interenga inghelical wheels revolubly carried inside. the casing, and the axes of which are parallelwith the axis of the grinding wheel,

meanswhereby theleadsorew controls the ro tation of the first helical wheel, means for preventing the axial shifting of the first helical wheel, means whereby the second helical wheel is adapted to, slide longitudinally of its axis, means whereby the spindle is constrained to revolve alternatingly in either direction, two cams fittedside by side over the second helical wheel in planes adapted. to register selectively with the axis ofrthe cutter-holder according to the axial position assumed by the second helical wheel under theactionof the thrust exerted in either direction on the latter by the revolving first helical wheel, said cams being mirror images of each other and including semi-circular operativesections and radial idle portions at the ends of their operative sections, the setting of the cams beingsuch as to align the generating lines corresponding to the beginning of the operative section on each cam, and a pusher member rigid with the cutter-holder and urged by the spring acting on said holder against the cam registering with the, axis of the cutter-holder, the operative section of each cam being adapted to produce an outward movement of the cutterholder against the action of itsspring during the registering with thecutter of the surfaces of the threaded, outline of the grinding wheel that face a predetermined axial direction.

ANDRE MOTTU. 

